Plastic Materials used for car parts such as bumpers normally have volume specific resistivity not lower than about 1010 Ω·cm, and it is difficult to directly apply paint onto such plastic shaped articles by means of electrostatic coating excelling in transfer efficiency. For this reason, conventionally an electrically conducting primer is applied onto such a material surface first, and thereafter top coat for coloring is applied by electrostatic coating (e.g., see JP Hei 6 (1994)-165966A).
Furthermore the plastic materials used for, e.g., car bumpers or the like normally have deep colors such as black. When light colored top coat or that of low hiding power is to be applied, said electrically conducting primer is required to have high hiding power or color of high value. With the view to meet such a requirement, various conducting paints using conducting pigments of relatively high value (antimony-doped type or non-antimony type pigments) have heretofore been proposed (e.g., JP Hei 9 (1997)-12314A, JP Hei 10(1998)-53417A). Whereas, antimony-doped type conducting pigments pose toxicity problem, and non-antimony type conducting pigments are very expensive.
JP 2003-231767A proposed use of conducting primer formed by adding cheap conducting carbon black pigment and specific aluminum powder as electrically conducting filler. This allowed formation of light grey primer coating and which has enabled electrostatic coating of light color top coat. However, where a formation of, in particular, a pearly multi-layered coating film of high degree of whiteness, i.e, having an L-value of whiteness on CIE color matching function of not less than 90, is intended, said conducting primer remains unsatisfactory. For conducting primer for which such high degree of whiteness is required, expensive white conducting pigment must be used.